Instant Hull Cleaner is formulated to begin working on contact to remove unsightly waterline stains. It is also very effective at removing rust stains or leaf stains from fiberglass or painted surfaces. It will not harm the surface being cleaned and is an ideal preparation for polishing the hull. Features Does not contain harmful acids, safe and easy to use. Quickly removes stains from water line. Excellent for use on fiberglass, metal and painted surfaces. Cleans scum lines and stains on boat hulls easily and effortlessly Safe For Use On Fiberglass And Painted Surfaces Instantly Removes Stains From Grassy Marine Growth, Rust, Scum Line, Fish Blood Etc. No Rubbing Or Scrubbing Directions Shake well. Apply using sponge or sprayer. Use of rubber gloves is recommended. Allow to remain on surface for 2 minutes then rinse with fresh water. Severely stained or dirty surfaces may require second application. For best results, use when temperature is over 50°F. To shine and protect newly cleaned hull, apply any of Star brite's Marine Polishes.